Mechanical Separation and Cleaning

A spiral separator separates round seeds from flat/irregular seeds using gravity on a stationary vertical spiral flight. Round seeds roll faster and develop centrifugal force pushing them over the outer flight rim. If inner flight radius is $r_1 = 0.15\text{ m}$ and outer rim radius is $r_2 = 0.30\text{ m}$, the ratio of outer to inner radius $r_2 / r_1$ is: